From: hasty@netcom.com (Amancio Hasty Jr) Subject: Re: ET4000/W32 and VESA VL-Bus Date: Fri, 18 Dec 1992 18:56:12 GMT
In article <1992Dec18.095906.3950@Informatik.TU-Muenchen.DE> roell@informatik.tu-muenchen.de (Thomas Roell) writes:
>>I thought that since EGA boards have been using double ported DRAM to
>>avoid this? Or are you saying 100MBs is for both ports? I have noticed
>>some ads saying their S3 board uses double ported DRAM so are we to
>>assume that most are not? If so then as you say this will instantly
>>destroy any speed a coprocessor can give as the only thing that matters
>>then is faster DRAM. I am no expert (as is obvius to the experts by
>>now) but I am just trying to get this picture. If ram access has always
>>got this refresh overhead (assuming a single port) then any board will
>>simply be limited by DRAM bandwidth.
>
>Yes, you are right, partially. Of course the serious graphics boards
>use all VRAM, which are dual ported RAMs specifically for graphics
>boards. They have a internal shift register for the screen refresh
>data and a random access port for the graphics engine. And of course
>those allow you to use the 100MB/sec (which was again just a sample
>number which seems to be realistic for the WD90C31) exclusively for
>the drawing operations. But the point was that somebody asked about
>the ET4000/W32, which is a DRAM based (and not VRAM based) solution.
>In my eyes, nothing justifies the usage of DRAMs for a graphics board if
>you want to use it for a GUI. The price difference is rather minor
>in those days.
>
>Also there are quite a number of S3 chips, which use EITHER VRAM or
>DRAM:
>
> 86C911 VRAM
> 86C924 VRAM
> 86C801 DRAM
> 86C805 DRAM
> 86C928 VRAM
>
>
>What I am saying is that for 1028x768 in 70Hz and 1280x1024 you should
>generally forget the DRAM based solutions. Even if they look good at
>benchmarks; most of these benchmarks used a 640x480 resolution,
All XS3 published benchmarks are run at 1024x768 clocked at higher
than 60 Hz. I obtained the results from netters because I don't
own a high resolution monitor. During candid, e-mail exchange I do
state my own benchmarks. In the future I will state the clock
frequency and the resolution.
Amancio Hasty
>where the screen refresh only takes 25MB/sec, and the available
>bandwidth for graphics operations is quite the same as for VRAM based
>solutions. But if you use the DRAM based boards at 1024x768, 70Hz,
>you'll see the difference.
>
>- Thomas
>
>--
>-------------------------------------------------------------------------------
>Das Reh springt hoch, e-mail: roell@sgcs.com
>das Reh springt weit, #include <sys/pizza.h>
>was soll es tun, es hat ja Zeit ...
-- Amancio Hasty | Home: (415) 495-3046 | ftp-site depository of all my work: e-mail hasty@netcom.com | sunvis.rtpnc.epa.gov:/pub/386bsd/incoming